Gas plating of synthetic fibers



May 30, 1961 H A. TOULMlN, JR

GAS PLATING OF SYNTHETIC FIBERS Filed May 14, 1958 INVENTOR HA REY A.TOL/LM/N JR.

Q BY

ATTORNEY5 United States Patent GAS PLATIN G 0F SYNTHETIC FIBERS Harry A.Toulmin, Jr., Dayton, Ohio, assignor, by mesne assignments, to UnionCarbide Corporation, New York, N.Y., a corporation of New York FiledMar. 14, 1958, 'Ser. No. 735,193

2 Claims. (Cl. 118-48) This invention relates to the metal plating offibers, fabrics and the like, and particularly to fibers and fabricswhich are made of natural or synthetic resins and which fibers tend to.soften or change physically when subjected to temperatures ordinarilyrequired for effecting the metal plating operation.

This application is a continuation-in-part of application Serial No.437,085 filed on June 16, 1954 now Patent No. 2,859,130.

This invention is especially adapted for metal plating of natural and/orsynthetic resin fibers or mixtures thereof, or fabrics woven orfabricated therefrom, and which fibers or fabric tend to deteriorate,discolor or otherwise change physically when subjected to relativelyhigh temperatures, and such as are generally employed in gaseous metalplating.

The invention is of particular utility for gaseous metal plating ofsynthetic fibers or fibrous masses such as are made principally ofsynthetic fibers or filaments, for example, nylon, Dacron, Orlon, Dynel,Acrilan, Saran, Vinyon and the like.

The invention will be described with more particularity as fibers orfilaments of continuous length,'but it will be understood asaforementioned that such fibers or filaments may be in the form offabricated products such as fabrics, mats, either woven, matted orotherwise formed into articles which can be subjected to gaseous metalplating.

It is an object of the invention to provide a method and apparatus whichcan be employed to effect metal plating of fibers, filaments and thelike by bringing the same in contact with a suitable heat-decomposablegaseous metal compound or mixture of such compounds and employingtemperatures sufiiciently high to cause decomposition of the gaseousmetal compound and deposition of the metal constituents thereof onto thesurface of the fibers without causing softening or injury to the fibersthus treated.

Another object of the invention is to provide a method of treatingfibers composed of synthetic resins and the like and which have arelatively low softening or melting point whereby the same can begaseous metal plated even at temperatures above their softening point.

Another object of the invention is to provide an improved method oftreating fibers, especially synthetic resinous fibers, so as to make. itpossible to gasous metal plate them by limiting the period of time thatthe synthetic resinous fibers are in contact with the heatdecom-.

posable gaseous metal plating compound, and whereby the fibers are notsubjected to a temperature for long enough time to cause softening ormelting of the fibers.

Another object of the invention is to provide an apparatus whereinfibers of the character described can be gaseous metal plated, suchapparatus comprising a chamber for carrying out gaseous metal depositionin combination with means for drawing the fibers through the chamber ata predetermined rate which may 1. varied depending upon the fiberbeing'plated,

ice

A still further object of the invent-ion is to provide an apparatusthrough which fibers may be drawn as a continuous length fiber andsubjected to gaseous metal plating, provision being made to move one ormore fibers, filaments, or fabric formed of the fibers, therealongthrough said chamber at a predetermined speed, the duration of exposureof the fiber to the temperature in the gas plating chamber, and whichtemperature may be above the established softening point of theparticular fiber, being controlled and limited so as to preventdeterioration of the fiber during gaseous metal plating.

A still further object of the invention is to provide an improvedapparatus and method for treating the fibers, both synthetic andnatural, to gaseous metal'plating and wherein the heating of theheat-decomposable gaseous metal compound in contact with the fibers, andtime of exposure thereto is controlled so as to prevent softening ordeterioration of the fiber or fibers during gaseous metal plating of thesame. i

This and other objects and advantages will become apparent from thefollowing description and reference to the drawing, wherein oneembodiment of the apparatus and method of gas plating fibers isillustrated. A

In the drawings Figure 1 illustrates, in perspective anddiagrammatically, a suitable apparatus for gaseous metal platingcontinuous fiber lengths in accordance with this invention;

Figure 2 is a vertical sectional view taken through the apparatusillustrated in Figure 1, being taken substantially on the line 2-2 ofFigure 1;

Figure 3 is a cross-sectional view taken substantially on the line 3-3of Figure 2;

Figure 4 is a cross-sectional view taken substantially on the line 4-4of Figure 2; and

Figure 5 is a view in perspective, similar to Figure l, with theomission of the fiber drawing mechanism and illustrating a modificationthereof wherein multiple gaseous metal plating chambers and coolingmeans are provided for carrying out successive and continuous gasplating treatments.

Attempts heretofore made to metal plate fibers, both natural andsynthetic, have been unsuccessful, particularly where the fiber iscomposed of material such as synthetic resin or organic or animalsubstances which tend to soften or deteriorate at the temperaturerequired for effecting the gaseous metal plating. The plating operationutilizing heat-decomposable metal compounds requires that thetemperature be raised high enough to cause the gaseous metal compound todecompose and deposit the metal constituent on the fibers. Eachheatdecomposable metal compound has a temperature at which decompositiontakes place. However, decomposition may take place slowly at a somewhatlower temperature or while the vapors are being heated up through aparticular range. For example, nickel carbonyl almost completelydecomposes at a temperature in the range ,of about 375 F. to 400 F. Thiscarbonyl, however, starts to decompose slowly at about F. anddecomposition continues during the time of heating from about 200 F. to380 F. A large number of metal carbonyls and hydrides also becomeeffectively and eflici'ent- 1y decomposed at a temperature in the rangeof 350 to 400 F. When working with most metal carbonyis it is preferredto operate. in a temperature range of about 3,7:5" F. to 450 F.

As will be seen, in order to deposit metal coatings on the fiber orfabric materials exposed thereto, it is necessary that the same besubjected to a temperature in the general decomposition range of thegaseous metal compound used to 'efiect the metal plating, a f

This has presented a very difliclilt. Problem which, insofar as isknown, has not been solved heretofore.

The present invention provides an apparatus and method for achievingthis.

In accordance with the preferred method the fiber, either in the form ofcontinuous length filaments of fabric, is subjected to a pro-warmingtreatment and then drawn through a gaseous metal plating chamber whereinthe same is subjected to gaseous metal plating and immediatelythereafter the fiber is cooled by moving the same through arefrigerating chamber. The fiber or fabric which may be made ofsynthetic resin having a softening or melting point below thetemperature of gaseous metal plating, is prevented from deterioratingduring the gaseous metal plating by limiting the period of time in whichthe fiber is subjected to gaseous metal plating. Thus, by subjecting thefibers to a controlled time of treatment a flash gaseous metaldeposition may be effected without bringing about injury or physicalchange of the fibers or fabric material being treated.

In accordance with the process, a stream of gaseous material is broughtin contact with the fiber, preferably pre-warmed and the gaseous metalplating carried out before the fiber becomes heated to a temperaturehigh enough to cause deterioration. The gaseous plating atmosphere maybe formed by mixing an inert gas with the vapors of a volatile metalcompound which is heatdecomposable or by atomizing a liquid metalcompound into a blast of hot inert gas or other equivalent method whichprovides a substantially gaseous metal for deposition onto the fibers.

As the inert gas there may be used carbon dioxide, helium, nitrogen orthe like which is inert to the gaseous metal compound and to the fibersbeing treated.

Metal to be deposited may be introduced as gaseous metal carbonyls orvaporized solutions of the metal carbonyls, in readily vaporizablesolvents, for example, petroleum ether or the like, also nitroxylcompounds or hydrides may be used such as nitrosyl carbonyls, metalhydrides, metal alkyls, metal halides, and the like.

Illustrative compounds of the carbonyl type are nickel, iron, chromium,molybdenum, cobalt, titanium, zirconium, and mixed carbonyls.

Illustrative compounds of other groups are the nitroxyls, such as coppernitroxyl; nitrosyl canbonyls, for example, cobalt nitrosyl carbonyl;hydrides, such as antimony hydride, tin hydride; metal alkyls, such aschromyl chloride; and carbonyl halogens for example, osmium carbonylbromide, ruthenium carbonyl chloride, and the like.

An important factor which results in the successful operation of themethod and apparatus for gaseous metal plating the fibers and fabrics ofthe character afore- .mentioned, is that of controlling the speed of thepassage of the fiber material through the gaseous plating chamber. Forexample, nylon softens at about 320 F. whereas Orlon softens at a highertemperature, for instance about 450 F. Saran becomes soft at about 260F. Accordingly, the speed of travel of the fibers through the apparatus,especially through the gaseous metal plating chamber, is controlled sothat at no time do the fibers themselves reach a temperature such as tocause them to soften or deteriorate.

The speed or duration of time in which the fibers. are subjected togaseous metal plating depends upon the fiber being treated. Further,where the time allowed for gaseous metal plating of the fiber isinsutficient to deposit the required thickness of metal coating on thefiber, then the fiber is returned for successive plating treatments andpassed through multiple gaseous metal plating chambers, as illustratedin the drawings.

Referring to the drawing, and particularly to Figures 1 and 2, there isdisclosed an embodiment of the invention wherein the fibers to 'beplated are drawn from one or more spools 12 and moved first through apreheatingchamber 14. This chamber is suitably heated,

as by the electrical heating elements 16, arranged around the walls ofthe chamber and so as to encompass the fiber drawn therethrough. Heatingelements 16 are connected to a source of electric current by leads 18and 19. The temperature of the pre-heating is preferably controlled by arheostat 20 actuated by a thermocouple 21 disposed in the chamber 14 andelectrically connected thereto. After the fiber has been drawn throughthe preliminary heating chamber 14 it is passed into the gaseousdecomposition metal plating chamber 24 wherein the same is subjected togaseous metal deposition. Thereafter the fiber is moved along throughthe cooling chamber 26 and thence over the guide pulleys 28, 29, 31 tothe storage spools 33 and 34.

To control the speed at which the fibers are drawn through the gaseousmetal chamber and associated heating and cooling chambers, a variablespeed motor 40 is utilized. This motor is arranged for variable speedoperation which may be accomplished by the use of a temperature actuatedrheostat 42. The speed or r.p.m. of the motor 40, as thus controlled, isarranged to drive the pulley 44 through the V-belt 45. Difierent speedsmay also be provided through the use of different diameter drivenpulleys operated by the motor 40 if desired. Pulley 44 is, in turn,drivingly connected to the pulleys 46 and 48 by means of the V-belts 50and 51 respectively.

The temperature and speed control means 42 are connected to thethermocouple 60 which is arranged in the gaseous metal plating chamber,as illustrated in Figure 1 and Figure 2, whereby the speed of the motormay be increased or decreased depending upon the temperature in thegaseous plating chamber. Thus, by setting the temperature controlmechanism 42 in accordance with the temperature desired in the gaseousmetal plating chamber,

,the apparatus may be operated so as to maintain the temperature andspeed of movement of the fiber through the gaseous chamber substantiallyconstant for any particular setting.

The gaseous metal deposition chamber 24 is suitably heated as by the useof resistance coil 65, the same being arranged around the chamber so asto evenly heat the same and bring about decomposition of the gaseousmetal compound introduced therein. The gaseous metal compound admixedwith inert carrier gas, e.g. carbon dioxide,

nitrogen, helium or the like, are introduced to the plating chamber 24through a conduit 68 and the spent gases, including unused metalcompound, are withdrawn through a conduit 70 and to a condenser 79, thegaseous metal compound being restored as a liquid in a tank or container78 which is connected through conduit 80 to the vaporizer 75 from whichit is returned through the conduit 68 to the gaseous metal platingchamber, as described.

The cooling chamber 26 comprises a coil which is arranged in the chamber87 through which the fiber is drawn after its passage through thegaseous plating chamber. Arranged around the cooling coil 85 isinsulating material 89 which may consist of mineral glass wool or thelike insulating material. Cooling fiuid is admitted to the coil 85through the conduit 91 and withdrawn therefrom through the conduit 93.

To prevent seepage of gaseous metal compound from the plating chamber 24through apertures at the opposite ends, as at 95 and 96, which permitsthe entrance and egress of the fibers, inert gas such as carbon dioxideis admitted through the conduits and 102 to the closure chambers 103 and104 which are arranged about these apertures. This inert gas ismaintained at a slightly higher pressure than that inside the gaseousplating chamber, thus preventing the gaseous metal compound from passingout through these apertures.

In the modification illustrated in Figure 5, the apparatus is of similarconstruction as illustrated and described in Figures 1 and 2, and thesame reference characters are pp ie tad s snate t e me- IP h Parti ul rm ifi cation three gaseous plating chambers 24a, 241;,and, 24c areutilized toef fect a triple flash metal plating of the fibers.Whereadditional gaseous metal treatment is desired, a plurality ofgaseous metalplating chambers may be employed with interposed coolingchambers whereby the process may be carfied out to providemultiple-gaseous plating treatment. In this manner, the fibers may besubjected to any desired number of gaseous metal plating treatments toproduce metal coating of a predetermined thickness. 7

In a plat ng with nick ar on l to p s t nickel me on o g nic q filamets. ncr n th mperature of the Ni(CO) vapor up to about 350 F. (maximum)increases the thermal decomposition rate of Ni(CO) Above 350 F.(approximately) no significant decomposition rate increaseoccurs, e.g.it can be regarded practically as an instantaneous reaction.

On an organic fiber, as in the process of this invention, at 350 F. theendothermic instantaneous" decomposition of Ni(CO) to give Ni thereonresults in a cooling of the fiber or loss of fiber heat so that thedecomposition of Ni(CO) Ni+CO gradually decreases to a very lowimpractical rate. Accordingly, since only a small amount of heat(particularly at 350 F.) can be put into a filamentous organic fiber, itfollows that only a very minute amount of Ni(CO) will be decomposed forthis quantity of filament heat.

It is, therefore, necessary to reheat and replate onto the fibers byalternately moving them through a series of heater-plater chambers orassembly, as illustrated in the drawings, where the amount of nickeldeposited onto the fibers and the fiber temperature are directly relatedto the number of alternate heating and plating chambers. Thisrelationship may be indicated as follows- Amount of nickel per unitweight of fiber=Number of alternate heating and plating chambersmultiplied by the fiber temperature It is, therefore, apparent that byincreasing the number of alternate heating and plating chambers to alarge figure (50-200) the fiber temperature may be lowered to a pointwhere thermally delicate fibers such as Dynel, or nylon can besatisfactorily plated with adequate amounts of nickel. This is based ona constant through-put rate through the plating apparatus.

The following examples illustrate the process of gaseous metal platingdifferent fibers with various heat-decomposable gaseous metal compoundsas described.

Example I Fibers of nylon were drawn through the apparatus as described,and subjected to a preliminary heat treatment of 250 F. Thereafter thesynthetic fibers are drawn through the gaseous metal plating chamber andsubjected to a temperature of 375 F. The gaseous metal plating materialconstitutes nickel carbonyl diluted with carbon dioxide gas, the rate ofgas fiow being maintained at approximately 4 liters per minute at atemperature of 78 F. and 125 mm. Hg. The fiber in the gaseous metalchamber was drawn through the chamber at a rate of 1 linear foot persecond, and such as to expose the ,fiber to gaseous metal treatment forapproximately 3 seconds. Where the plating chamber is of a length ofapproximately 3 feet, this provides a gaseous plating time of 3 seconds,being insutficient to heat up the fiber to a temperature such as tocause it to soften. Thereafter the gaseous metal treated fiber is drawnthrough the cooling chamber so as to quickly cool the fiber and preventit from retaining the residual heat and causing distortion ordeterioration thereof. The cooling chamber was maintained at atemperature of approximately 32 F. by cireulating brine through thecooling coil.

The process p ovide nylon fibers havin a c at ng o n cke metal, h hi nes t h seat ng b insibttwss about 0.00002-0.00004 inch. Where a greaterthickness of the metal coating is desired, the fiber is subiected torepeated gaseous metal plating cycles of tieatnients as aforementioned,For carrying out a plurality of succw sive gaseous metal treatments, theapparatus illustrated in Figure 5 may be used.

Example II In this instance Orlonfiber iscoated with iron utilizing roncarbony s he heat d comp able aseonsmetal mpound. The fiber s rawn h o she apparatus similarly as described in Example I, being subjected mapreliminary heat treatment of 350 F.- The gaseous metal deposition inthe plating chamber is conducted in this instance at 475 F. Theatmosphere in the plating chamber consists of nitrogen containing about2% by volume of iron carbonyl. The duration exposure of the fiber in thegaseous metal plating chamber to this temperature is held toapproximately 10 seconds and the speed of the fiber was accordinglyadjusted so as to provide for this plating time in the gaseous metalplating chamber.

Inasmuch as Orlon has a higher softening temperature, namely about 450F. as compared with'about 320 F. for nylon, accordingly Orlon fibers maybe exposed for a somewhat longer length of time in the plating chamberwithout injury.

After passing the fibers through the plating chamber and cooling chamberas in Example I, the resultant Orlon fibers are provided with a metalcoating of iron having a film thickness approximately 0.00004 to 0.00006inch.

Example III In this instance a fabric made of Saran is nickel coatedutilizing nickel carbonyl similarly as in Example I, by passing the samethrough the heating and gaseous metal plating chamber at a speed such asto complete the exposure of the fiber in the gaseous metal chamber in 5seconds. The temperature for carrying out the gaseous metal depositionof the nickel being held at approximately 375 F.

In this instance the thickness of the nickel metal coating on the fiberapproximates 00004-000006 inch.

As will be understood, other gaseous metal compounds may be employed, ormixtures thereof, to produce the desired metal coating on the fiber orfabric being treated.

It will be understood that this invention is not to be restricted to thespecific fibers mentioned and examples given above, but that it issusceptible to various modifications and changes which come within thespirit and scope of this disclosure and as more particularly set forthin the appended claims.

What is claimed is:

1. Apparatus for gas plating metal on heat sensitive organic fibermaterial, and which tend to soften under prolonged heating at 350 to 475F., said apparatus comprising a series of gas plating and coolingchambers, means including a variable speed motor for advancing saidfiber material through said series of chambers, each of said gas platingchambers being connected directly with a cooling chamber whereby saidfiber is quickly cooled following the gas plating operation, a source ofheat-decomposable metal bearing compound admixed with inert carrier gas,means for heating said organic fiber material, means for directing ablast of said inert carrier gas containing the heat-decomposable metalcompound onto said fiber, and means for controlling the speed ofoperation of said variable speed motor and resultant speed at which saidfiber material is moved through said apparatus.

2. Apparatus for gas plating metal on heat-sensitive organic fibermaterial, and which tend to soften under prolonged heating at 350 to 475F., said apparatus comprising a plurality of gas plating chambers withinterposed cooling chambers, means including a variable Speed main,

mechanismfor advancing said fiber material through said plurality ofchambers, each of said gas plating chambers .bcing contiguouslyconnected with a cooling chamber whereby said fiber is immediatelycooled following the gas plating operation, a source ofheat-decomposable metalbearing compound-admixed withinert carrier gas,means for heating said organic fiber material, means for introducingsaid inert-carrier gas containing the heatdecornposable metal compoundinto said plating chamspeed at which said fiber material is moved;through said apparatus. 1

References Cited in the file of tliisipatent UNITED STATES PATENTS Aug.13, 1946 2,616,165 Brennan Nov, 4, 1952 2,656,283 Fink et a1. Oct. 20,1953 2,785,651 Pawlyk Mar. 19, 1957 2,789,064 Schladitz Apr. 16, 19572,859,130 Toulmin Nov. 4, 1958 2,884,337 Homer et al. Apr. 28, 19592,897,091

Homer et a1. July 28, 1959

1. APPARATUS FOR GAS PLATING METAL ON HEAT-SENITIVE ORGANIC FIBERMATERIAL, AND WHICH TEND TO SOFTEN UNDER PROLONGED HEATING AT 350 TO475*F., SAID APPARATUS COMPRISING A SERIES OF GAS PLATING AND COOLINGCHAMBERS, MEANS INCLUDING A VARIABLE SPEED MOTOR FOR ADVANCING SAIDFIBER MATERIAL THROUGH SAID SERIES OF CHAMBERS, EACH OF SAID GAS PLATINGCHAMBERS BEING CONNECTED DIRECTLY WITH A COOLING CHAMBER WHEREBY SAIDFIBER IS QUICKLY COOLED FOLLOWING THE GAS PLATING OPERATION, A SOURCE OFHEAT-DECOMPOSABLE METAL BEARING COMPOUND ADMIXED WITH INERT CARRIER GAS,MEANS FOR HEATING SAID ORGANIC FIBER MATERIAL, MEANS FOR DIRECTING ABLAST OF SAID INERT CARRIER GAS CONTAINING THE HEAT-DECOMPOSABLE METALCOMPOUND ONTO SAID FIBER, AND MEANS FOR CONTROLLING THE SPEED OFOPERATION OF SAID VARIABLE SPEED MOTOR AND RESULTANT SPEED AT WHICH SAIDFIBER MATERIAL IS MOVED THROUGH SAID APPARATUS.